Process for the injection moulding of multi-layered articles

A process for the injection moulding of a multi-layered container having barrier properties using injection moulding apparatus, said container having a depth:width ratio of at least 0.75:1, said apparatus having a mould block with a core that is adapted to be inserted into a cavity of the mould block in a spaced-apart relationship related to the thickness and shape of the container to be moulded, said core having a tip that is comprised of an outer core and a centrally located plunger that moves independently of the outer core, the surfaces of the outer core and of the plunger forming the surface of the core when the core is located within the mould block, comprising the steps of:

• (a) clamping a self-supporting thermoplastic film over the cavity of the mould block said film being selected from (1) PVDC-coated polyethylene, (2) laminates of polyethylene/PVDC/polyethylene, (3) laminates of polyethylene/ethylene-vinyl alcohol/polyethylene, (4) laminates of polyethylene/polyvinyl alcohol/polyethylene, (5) laminates of polyethylene/PVDC/ethylene-vinyl acetate copolymer, (6) laminates of polyethylene/polyvinyl alcohol/ethylene-vinyl acetate copolymer, and (7) laminates of polyethylene/ethylene-vinyl alcohol/ethylene-vinyl acetate copolymer and further being capable of being stretched to conform to the shape of the core that is to be inserted into the mould block.
• (b) substantially uniformly stretching the film by sequentially stretching the film in two stages within the mould block using the core, with the plunger preceding the outer core into the mould block, such that (i) the plunger stretches the thermoplastic film, and (ii) the outer core further stretches the film, the plunger retracting into the outer core as the outer core enters the cavity of the mould block, thereby forming the surface of the core in the mould block;
• (c) closing the mould block and core, with excess film, being trimmed off substantially simultaneously therewith using a serrated blade, the serrated blade located on the core and entering a recess in the mold block upon closure;
• (d) injecting molten thermoplastic polyolefin into the mould between the film and the surface of the mould cavity, said polyolefin being bonded to the film such that the container is formed with polyolefin on its outer surface thereof and the polyethylene of the film on its inner surface thereof;
• (e) allowing the container so moulded to cool to below the heat distortion temperature of the moulded container;
• and
• (f) opening the mould block and core and removing the moulded container;
• said film having different barrier properties than the thermoplastic polyolefin with respect to at least one of oxygen, hydrocarbon liquids, and water.